Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Semiconductor devices perform a wide range of functions such as analog and digital signal processing, sensors, transmitting and receiving electromagnetic signals, controlling electronic devices, power management, and audio/video signal processing. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, diodes, rectifiers, thyristors, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, application specific integrated circuits (ASIC), power conversion, standard logic, amplifiers, clock management, memory, interface circuits, and other signal processing circuits.
A semiconductor wafer includes a base substrate material and plurality of semiconductor die formed on an active surface of the wafer separated by a saw street. Many applications require the semiconductor die to be reduced in height or thickness to minimize the size of the semiconductor package. Testing and inspection of the semiconductor wafer is important for quality assurance and reliability. Testing typically involves contacting a surface of the semiconductor wafer with a test probe. Yet, for large thin semiconductor wafers, wafer test probing often leads to breakage or damage from probe pressure on the thin wafer surface, as well as wafer handling and wafer warpage. The thin semiconductor wafers are subject to warpage. A warped thin semiconductor wafer is difficult to test because the test probes may not make contact with the warped surface.
In some cases, wafer test probing is performed prior to wafer thinning because the large thin wafers, e.g., wafers with a diameter of 150-300 millimeters (mm), may be warped beyond the test probe contact tolerance, or because the thin wafer surface cannot handle the invasive nature of the test. Wafer testing prior to wafer thinning is incomplete because certain features that are added post-wafer thinning, e.g., backside metal, are not present for the test. In addition, for MOSFETS or wafers with through silicon vias, the current flows through the silicon and out the backside of the thinned wafer, i.e. through the back metal. Testing such devices is impractical for full-thickness wafers. The thickness of the wafers also affects the electrical performance. A thicker T-MOSFET wafer has more resistance than a thin wafer since the current must pass through more silicon. Wafer testing and inspection before all features are present reduces quality assurance, and adds manufacturing cost because an untested die must be assembled before functionality can be confirmed.